Koussevitzky wrote him letters imploring him to send the 8th symphony, but Sibelius would routinely delay him, even lying that it was finished. Some fragments were published and played in 2011, but it's only just enough to wonder what could have been...

Most famous tone poem

To avoid Russian censorship, Finns often changed the name of the piece to disguise it, the most hilarious example being 'Happy Feelings at the awakening of Finnish Spring.'

Number of Concerti

Ah, you're a smart one, you are.

Instrument for which he wrote the most concerti

Hilary Hahn's recording is the best. Crystaline, keen, calculating...most importantly, evocative of the Scandinavian landscape and wintertime. Plus, that huge shift in the third movement? Flawless. End of discussion.